CAD Designs for Bioprinting: Lattices

Creating 3D designs for bioprinting requires certain considerations to ensure an optimal tool path that will work with complex materials and cell types. Lattices are a common design in bioprinting for testing new materials and parameters in bioprinting, creating a simple 3D porous structure that provides for nutrient transport and waste export. Watch this video or read the notes below on what to keep in mind to create optimal lattice designs for your Allevi.

CAD Design of Your Lattice

The first file to create for bioprinting is an .stl file. This file can be developed on any number of CAD (computer-aided design) programs. TinkerCAD is a great program to start with if you do not have any prior CAD experience and only need to create simple objects. Another great program that offers a free trial version is Autodesk Fusion 360. The directions below are based on the program Solidworks, which is provided to many students for free through their universities. However these directions can be followed generally for any CAD program that allows the user to save files in .STL format.

Design Considerations for Your Lattice

To create an optimal tool path, it is best to create lines with the thickness of your needle diameter and height of your desired path height in slicing. Slicing the file will occur after designing in the CAD program. “Slicing” involves creating the tool path that your bioprinter will follow and will have a large impact on the success of your print. Usually, the height and thickness are designed to be equal.

For each layer, you want to create a single connecting line. This line, if drawn, should be able to be created without lifting a pen or crossing over any previous lines. Using this design method, the slicing program will be able to create only one tool path for that layer. See some images and videos below for examples of a four layer lattice designed with this method. The image shows the final construct with 4 layers assembled. Watch the video for a step-by-step guide to design this lattice.

So what are some examples of what not to do? Try avoiding creating a “checkerboard” design like below, which may confuse the slicing program and will not create the best tool path. Likewise, avoid connecting all interior lines with an outside border, which may also cause sub-optimal tool paths during slicing.

Slicing Your Files

Go ahead and try slicing the three sample files designs above in Slic3r to better understand the effects of your CAD design on your final printed construct. Make sure the path height and extruder nozzle sizes are the same as your line thickness and height. For the examples below, this value is 0.2 mm. We suggest a speed of 2 mm/s. (Download the Slic3r settings here)